A nonliving anticoccidiodal vaccine, prepared from the spherule phase of Coccidioides immitis, has been developed by one of the co-principal investigators. It is efficacious in mice in that it confers upon these animals a capacity to survive challenge doses well in excess of 200-fold those lethal to nonvaccinated animals. Similarly in Macaca irus monkeys the induced protective response enabled the animals to withstand a severe potentially lethal challenge given by the respiratory route. However in mice, in monkeys and in man, vaccination produced only irregular humoral and/or cutaneous sensitivity manifestations of immunity. And although those animals that develop no detectable humoral or sensitivity responses after immunization appear to be fully as well-protected as those animals that do, the very irregularity of the detectable responses poses problems in a human vaccination trial. It is the purpose of this study to investigate and, if possible, modify the vaccine or the methods by which it is administered in order to augment the readily detectable manifestations of vaccination.